1. Field of the Invention
The present invention relates to a standard force realization apparatus, and more particularly to a standard force realization apparatus using a superconducting flux quantum, which is capable of generating force proportional to a flux quantum number by including a micron-sized superconducting annulus or superconducting quantum interference device in an ultra-sensitive cantilever.
2. Description of the Related Art
As industries have been remarkably developed, precision of measurement standard has been of importance. Force measurement is widely performed from the aerospace industry, the heavy chemical industry and the plant industry which treat a load of at least several tens of mega-Newtons (MN) to the ultra-precision weighing machine field which measures a weight of several tens or less of micrograms and an atomic force microscope which senses nano-Newtons (nN). Every country uses a deadweight force standard machine, which is developed by a national measurement institute, as a national standard mainly in the 5 N˜500 kN range.
A force realization apparatus is used in the force standard machine, which provides force generated by a weight to a force measurer and checks how precise the force measurer is.
Recently, due to remarkable improvement in measurement sensitivity, force measurement has become a useful and essential probe for leading-edge nano/bio-researches, which cover protein folding studies, high-integration data storage, nanoscale imaging, non-Newtonian gravitation measurement, and many others.
The force detection limit keeps getting lowered, for example, to an atto-Newton (10−18 N) (aN) level in magnetic resonance force microscopy capable of reading a single electron spin.
However, no direct system international (SI)-traceable force realization has been established even at below 1 Newton level. The prevailing deadweight method, which creates gravitational force using standard weights, obviously becomes no longer valid below micro-Newton level. In the national institute of standards and technology of United States of America, a microforce realization and measurement project for generating force of 10 micro-Newtons or less using an electrical method has been proposed. Therein, the force is created between two electrodes of a capacitor having a constant voltage and is represented by electrical units such as a voltage. The electrical units are traced to their standards based on Josephson and quantized Hall effects.
However, at the nano-Newton or pico-Newton level, no force realization method for standard has been suggested despite needs for precision measurements of force. In addition, it casts a striking contrast to the case of the electrical units such as the voltage that no attempt has been tried to directly use quantum phenomena in realizing a mechanical force.